At diagnosis, patients with small cell lung cancer (SCLC) have a high rate of brain metastasis (around 20%), and this number rises to >50% at 2 years. Disease which has spread to the brain generally has a poor response to chemotherapy and brain radiation therapy. Prophylactic cranial irradiation (PCI) is radiation given to the brain to prevent the development of brain metastases. It is effective in limited-stage SCLC and does not typically lead to an increase in the risk of late neurologic problems. This study was performed to determine if PCI impacts outcomes in patients with extensive stage SCLC who have responded to chemotherapy.

Patients with extensive stage SCLC received 4 to 6 cycles of chemotherapy, and if they had any response to chemotherapy, were then randomized to either PCI or no PCI. Side effects were generally mild in the PCI arm with headache, nausea/vomiting, fatigue, and skin reactions being the most common. PCI significantly reduced the rate of symptomatic brain metastasis, with rates at 1 year of 15% vs. 40% in the non-PCI versus PCI arms, respectively. PCI also improved overall survival (survival with or without disease progression) at 1 year: 27.1% in the PCI arm vs. 13.3% in the non PCI arm. There was no difference between the two arms in disease progression outside of the brain. This trial should change the standard of care in this disease, and the authors conclude that patients with extensive stage SCLC should routinely receive PCI.